A method of the above kind, an internal combustion engine of the above kind and a control apparatus of the above kind are generally known from internal combustion engines having exhaust-gas recirculation, for example, from a so-called gasoline-direct injection or a so-called diesel direct injection or also from a so-called intake manifold injection, each having exhaust-gas recirculation.
In these internal combustion engines, a catalytic converter is provided for purifying the toxic substances arising with the combustion of the fuel. The catalytic converter is, for example, a so-called three-way catalytic converter or an NOx storage catalytic converter or an oxidation catalytic converter. These catalytic converters require a specific temperature, for example approximately 300° C., for an optimal operation.
A possible operating mode of the internal combustion engine is the so-called overrun operation which is better characterized as a push operation since the internal combustion engine generates no torque in overrun operation; instead, the engine is driven by the rolling motor vehicle. In overrun operation, no fuel is supplied to the engine although the rpm of the engine is greater than the idle rpm.
For overrun phases which are longer in time, there is the possibility that the catalytic converter slowly cools and moves out of its work range. This results because, in overrun operation, no combustion of fuel takes place and therefore no new hot exhaust gas arises. The cooling out of the catalytic converter has, however, the consequence that the exhaust gases in engine operation after an overrun phase can initially no longer be optimally purified.